1. Field of the Invention
The present invention relates to a coating apparatus and method, and more particularly to a coating apparatus and method in which a plurality of layers are formed on a strip-shaped base material in a state of continuously travelling.
2. Description of the Related Art
As an example of a conventional coating apparatus and method, there has been proposed a coating apparatus and method, wherein in a manufacturing process of planographic printing plates, a desired coating liquid is coated to a strip-shaped aluminum plate (a so-called aluminum web) which serves as a base material (for example, see Japanese Patent Application Publication (JP-B) No. 58-4589).
A planographic printing plate is ordinarily manufactured by the procedure in which a support web is produced by graining one surface or both surfaces of an aluminum web in accordance with an ordinary method, and an anodic oxide layer is formed on the grained surface of the support web, and thereafter, a plate making layer (that is, a lower layer) which is a single-layer or multi-layered photosensitive layer or heat-sensitive layer is formed thereon, and an antioxidant layer (that is, an upper layer) is formed on the surface of the plate making layer.
In a planographic printing plate having a multi-layered plate making layer or a planographic printing plate having an antioxidant layer on a plate making layer, generally, respective layers are formed one by one. Ordinarily, these layers are each formed by coating thereto a coating liquid such as a photosensitive-layer forming liquid containing a photosensitive resin, a heat-sensitive layer forming liquid containing a thermal polymerization resin, and an antioxidant-layer forming liquid containing, as the principal component, a polyvinyl alcohol aqueous solution, and thereafter, drying the coated coating liquid. At this time, in a case in which an uncoated portion with no photosensitive-layer forming liquid coated thereto occurs for any reason, an anodic oxide layer of the support web is exposed at the uncoated portion.
The antioxidant-layer forming liquid has excellent wettability to the photosensitive layer, but does not necessarily have much excellent wettability to the antioxidant film. However, in conventional coating apparatuses and methods, even if the uncoated portion exists, the antioxidant-layer forming liquid is continuously coated in this state. Therefore, there exists a problem that poor coating of the antioxidant-layer forming liquid occurs in the uncoated portion, thereby resulting in the antioxidant-layer forming liquid be nonuniformly coated. Then, if once poor coating of the antioxidant-layer forming liquid occurs, even when poor coating in the photosensitive-layer forming liquid is solved and the photosensitive-layer forming liquid is normally coated, poor coating of the antioxidant-layer forming liquid cannot be solved.